MicroRNAs (miRNAs or miRs) are small non-coding RNAs expressed in animals and plants. They regulate cellular function, cell survival, cell activation and cell differentiation during development.7;8 
MicroRNAs are a small non-coding family of 19-25 nucleotide RNAs that regulate gene expression by targeting messenger RNAs (mRNA) in a sequence specific manner, inducing translational repression or mRNA degradation depending on the degree of complementarity between miRNAs and their targets (Bartel, D. P. (2004) Cell 116, 281-297; Ambros, V. (2004) Nature 431, 350-355). Many miRs are conserved in sequence between distantly related organisms, suggesting that these molecules participate in essential processes. Indeed, miRs are involved in the regulation of gene expression during development (Xu, P., et al. (2003) Curr. Biol. 13, 790-795), cell proliferation (Xu, P., et al. (2003) Curr. Biol. 13, 790-795), apoptosis (Cheng, A. M., et al. (2005) Nucl. Acids Res. 33, 1290-1297), glucose metabolism (Poy, M. N., et al. (2004) Nature 432, 226-230), stress resistance (Dresios, J., et al. (2005) Proc. Natl. Acad. Sci. USA 102, 1865-1870) and cancer (Calin, G. A, et al. (2002) Proc. Natl. Acad. Sci. USA 99, 1554-15529; Calin, G. A., et al. (2004) Proc. Natl. Acad. Sci. USA 101, 11755-11760; He, L., et al. (2005) Nature 435, 828-833; and Lu, J., et al. (2005) Nature 435:834-838).
There is also strong evidence that miRs play a role in mammalian hematopoiesis. In mice, miR-181, miR-223 and miR-142 are differentially expressed in hematopoietic tissues, and their expression is regulated during hematopoiesis and lineage commitment (Chen, C. Z., et al. (2004) Science 303, 83-86). The ectopic expression of miR-181 in murine hematopoietic progenitor cells led to proliferation in the B-cell compartment (Chen, C. Z., et al. (2004) Science 303, 83-86). Systematic miR gene profiling in cells of the murine hematopoietic system revealed different miR expression patterns in the hematopoietic system compared with neuronal tissues, and identified individual miR expression changes that occur during cell differentiation (Monticelli, S., et al. (2005) Genome Biology 6, R71). A recent study has identified down-modulation of miR-221 and miR-222 in human erythropoietic cultures of CD34+ cord blood progenitor cells (Felli, N., et al. (2005) Proc. Natl. Acad. Sci. USA. 102, 18081-18086). These miRs were found to target the oncogene c-Kit. Further functional studies indicated that the decline of these two miRs in erythropoietic cultures unblocks Kit protein production at the translational level leading to expansion of early erythroid cells (Felli, N., et al. (2005) Proc. Natl. Acad. Sci. USA. 102, 18081-18086). In line with the hypothesis of miRs regulating cell differentiation, miR-223 was found to be a key member of a regulatory circuit involving C/EBPa and NFI-A, which controls granulocytic differentiation in all-trans retinoic acid-treated acute promyelocytic leukemic cell lines (Fazi, F., et al. (2005) Cell 123, 819-831).
A frequent deletion and reduced expression of two miRs in B-cell chronic lymphocytic leukemia has been identified9. This discovery stimulated numerous articles documenting aberrant expression of miRs in head and neck carcinomas, small cell lung cancers, glioblastomas, breast cancers, chronic lymphocytic leukemia, and Burkitt lymphoma.9-12 More recently, a relationship between inflammation and miRs has been reported in macrophages.13 
In order to test for such disorders, tissue samples have been obtained in order to confirm the presence of such macrophages. In addition, until now, there has been no report demonstrating that microvesicles that circulate in the blood contain miRs.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.